Modeling of coastal infragravity waves using the spectral model WAVEWATCH Ⅲ
Modeling of coastal infragravity waves using the spectral model WAVEWATCH Ⅲ
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DOI：
10.1016/j.coastaleng.2021.104016
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发表时间：
2021-12
影响因子：
4.4
通讯作者：
Zhenjun Zheng;Xiaozhou Ma;Yuxiang Ma;Xuezhi Huang;Guo-hai Dong
中科院分区：
文献类型：
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作者：
Zhenjun Zheng;Xiaozhou Ma;Yuxiang Ma;Xuezhi Huang;Guo-hai Dong
预报近海次重力(IG)波对于预防IG波造成的沿海灾害至关重要。在这项研究中，比较评估了非结构WaveWatchⅢ(WW3)在预报沿海IG波方面的性能，考虑了数值方案、时间步长和IG源参数化方法的影响。使用安装在斯里兰卡南部海岸的三个声学传感器进行了波浪测量，其中两个安装在港口附近或港口内。对数值格式和时间步长的敏感性分析表明，显式格式与小时间步长相结合导致了IG波高的意外波动。然而，时间步长对隐式格式结合区域分解方法的性能影响可以忽略不计。一般来说，由经验公式法(震源M1)和二阶谱方法(震源M2)估计的IG源在再现IG波高方面表现相似。对于IG频谱，两个IG源都正确地预测了频谱密度的大小，但没有充分捕获频谱形状。M2可以提供更好的IG波能量的定向传播。港口内的IG波也受到了关注。由于模拟中缺乏与IG波相关的一些机制，港口内的IG波被低估了。当粗略地预报港内IG波的大小时，应采用M1。总体而言，非结构WW3可以有效地预报斯里兰卡南部沿海IG波的高度，与现场测量结果相比具有显著的相关性和可接受的误差。最后，对IG源M1进行改进，以消除WW3谱中IG和风浪频带之间的错误光谱间隙。
Forecasting coastal infragravity (IG) waves is crucial in preventing coastal disasters caused by IG waves. In this study, the performance of the unstructured WAVEWATCH Ⅲ (WW3) in predicting coastal IG waves is comparatively assessed using in-situ wave measurements, considering the effects of numerical schemes, time steps, and IG-source parameterization methods. The wave measurements are performed using three acoustic sensors installed at the coast of south Sri Lanka, with two being near or inside a harbor.Sensitivity analysis of the numerical schemes and time steps shows that the explicit scheme combined with a small time step leads to unexpected oscillations of the IG wave height. However, the time step has a negligible influence on the performance of the implicit scheme combined with the domain decomposition method. Generally, IG sources estimated from the empirical formula method (source M1) and the second-order spectrum method (source M2) perform similarly in reproducing the IG wave height. Regarding the IG frequency spectrum, both the IG sources properly predict the magnitude of the spectral density, but the spectral shapes are not adequately captured. M2 may provide a better directional spread of the IG wave energy. Attention is also paid to the IG waves inside the harbor. The IG waves within the harbor are underestimated, owing to the lack of some mechanisms related to IG waves in the simulation. M1 should be adopted when crudely predicting the magnitude of IG waves inside a harbor. Overall, the unstructured WW3 can effectively predict the coastal IG wave height in southern Sri Lanka, with significant correlation and acceptable errors, when compared with in-situ measurements. Finally, the IG source M1 is refined to remove the erroneous spectral gap between the IG and wind-wave frequency bands in the WW3 spectra when compared to the in-situ observed spectra.